| |
| Identifiers | |
|---|---|
3D model (JSmol) |
|
PubChem CID |
|
| |
| |
| Properties | |
| C5CoN53− | |
| Molar mass | 189.025 g·mol−1 |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
| |
Inchemistry, pentacyanocobaltate is the coordination complex with the formula [Co(CN)5]3−. When crystallized with a quaternary ammonium cation, it can be obtained as a yellow solid. Pentacyanocobaltate attracted attention as an early example of a metal complex that reacts with hydrogen. It contains low-spin cobalt(II), with a doublet ground state.
Aqueous solutions of pentacyanocobaltate are produced by the addition of five or more equivalents of a cyanide salt to a solution of a cobalt(II) salt. Initially this reaction produces insoluble cobalt dicyanide, but this solid dissolves in the presence of the excess cyanide. Pentacyanocobaltate forms within seconds.[1] When prepared using a quaternary ammonium (quat) cyanide, crystals can be obtained with the formula (quat)3[Co(CN)5]. According to X-ray crystallography, the salt features square pyamidal [Co(CN)5]3−.[2]
Solutions of [Co(CN)5]3− undergo a variety of reactions. The complex attracted attention in the 1940s for its reactivity toward hydrogen, which is now understood to produce a cobalt hydride:[1]
When allowed to stand as a dilute solution for several minutes, the complex reacts with water to give two Co(III) derivatives:
In concentrated solution, the complex dimerizes:
With benzyl chloride and related alkylating agents, Co(III) alkyls are formed:[3]
